1. Field of the Invention
The invention relates to medical devices for percutaneously accessing body lumens and, more particularly, to methods and devices for accessing the cardiovascular system. In one application, the invention relates to methods and devices for introducing and removing large balloon catheters and instruments, particularly intra-aortic balloon pumps, into and from a patient.
2. Description of the Related Art
A wide variety of diagnostic or therapeutic procedures involves the introduction of a device into the vasculature through a percutaneous incision at an access site. Such regions of the vasculature, preferred for access, include both the arteries and veins, typically at peripheral locations in the body. Typical access sites include the femoral arteries, and the iliac arteries. A percutaneous technique commonly known for such vascular access is the Seldinger technique. The Seldinger technique involves using a hollow needle to puncture the skin and gain access to the selected artery or vein. A guidewire is next placed through the hollow needle into the selected region of vasculature. The guidewire may be advanced to a target location in the vasculature, often more than 100 cm away from the access site. The needle is removed and a tapered dilator with a sheath and a central lumen in the dilator is advanced over the guidewire into the vasculature. The dilator is next removed and a guide catheter is advanced through the sheath over the guidewire. The guide catheter can be advanced all the way, or part way, to the target site. The guide catheter, following, or without, removal of the guidewire can be used for directing therapeutic or diagnostic catheters to regions of the vasculature and central circulation, including external and internal structures of the heart. A general objective of access systems, which have been developed for this purpose, is to minimize the cross-sectional area of the access lumen, while maximizing the available space for the diagnostic or therapeutic catheter placement therethrough. These procedures are especially suited for coronary angioplasty, stent placement, cerebrovascular coil placement, diagnostic cardiac catheterization, cardiac assist, and the like.
One type of cardiac assist procedure involves placement of an intra-aortic balloon pump (IABP) within the descending aorta of a patient and performing counterpulsation within the central circulation. The IABP procedure was originally developed by Dr. Adrian Kantrowitz in the late 1960s for use on surgical patients with the goal of improving coronary perfusion. Today, the procedure involves the steps of inserting a hollow needle, with a hemostasis valve affixed to its proximal end, into the femoral or iliac artery of a patient via a percutaneous puncture. A guidewire is next inserted through the hemostasis valve and the central lumen of the needle into the femoral or iliac artery. The guidewire is routed, under fluoroscopic control, cranially toward the heart until it reaches the aortic arch. The hollow needle is removed from the patient leaving the guidewire in place. A sheath, including a tapered tip central obturator or dilator having a hemostasis valve at its proximal end and further including a central guidewire lumen is routed over the guidewire, through the skin puncture, through the wall of the artery, and into the central lumen of the artery. The central obturator or dilator is removed. An intra-aortic balloon pump catheter is next inserted through the hemostasis valve, through the sheath, and into the artery where it is next advanced to the target site in the thoracic descending aorta. The IABP is operated to support, or augment, the patient's circulation until adequate cardiac function can be restored to allow weaning and removal of the IABP. Indications for IABP use include failure to remove from cardiopulmonary bypass, cardiogenic shock, heart failure, acute myocardial infarct, and support during high-risk interventional procedures such as percutaneous transluminal coronary angioplasty (PTCA), percutaneous heart valve placement, and coronary stent placement. The IABP is connected, at its proximal end, to a pumping and control console. An IABP pumps blood by alternate inflation and deflation within the aorta, using helium gas as the balloon inflation media, while being timed with the opening and closing of the patient's aortic valve so as to provide for optimal circulatory augmentation. Timing of the IABP cycle is generally triggered according to the patient's electrocardiogram, their blood pressure, a pacemaker (if present), or by a pre-set timer. An IABP can achieve as much as a 40% improvement in cardiac output with accompanying reductions in left ventricular stroke work and myocardial oxygen consumption. The IABP can be left in place for periods of hours to more than 2 weeks to allow restoration of natural cardiac function. The IABP can be removed from the patient by first deflating the balloon and then withdrawing the IABP until it is removed from the patient. The sheath is next removed and hemostasis is established using standard techniques for a vessel puncture wound.
Issues can arise, however, when the IABP is removed from the patient. Following deflation, the collapsed balloon, typically fabricated from a thin layer of inelastic polyethylene, may form a plurality of wings, or flattened, radially outwardly projecting structures that are relatively hard and sharp and may not fold neatly against the catheter shaft. Such balloon wings have been reported to cause disruption of vessel plaque during removal or pullback through the aorta, iliac and femoral arteries. This is especially problematic in very sick patients with significant vascular disease that involves plaque, mural thrombus, aneurysms, and other pathologies. The disruption of a region of plaque or thrombus can cause emboli to break free from the vessel wall, float downstream, and lodge within the lumen of smaller distal vessels, blocking blood flow, and resulting in ischemia and possibly tissue necrosis.
Suggested further reading related to the use of intra-aortic balloon pumps includes P. J. Overwalder: “Intra Aortic Balloon Pump (IABP) Counterpulsation”, The Internet Journal of Thoracic and Cardiovascular Surgery, 1999, Volume 2 Number 2 and “Counterpulsation: Historical Background, Technical Improvements, Hemodynamic and Metabolic Effects”, Cardiology, Volume 84, 1994, pp. 156-167.
It is desirable to protect the arteries, including the femoral and iliac arteries, from the IABP during removal. A need remains, therefore, for improved access technology, which allows a large diameter balloon catheter to be percutaneously or surgically introduced, endovascularly advanced to the descending aorta, pumped for a period of hours, days, or weeks, and then be removed without causing further injury or complications to the patient.